Field of the Invention
The present invention relates to print inspection of variable printing which performs printing while determining a variable object to use immediately before the printing.
Description of the Related Art
Recently, a print on demand (hereinbelow, referred to as POD) market has expanded with increase in speed and improvement of image quality of electrophotographic method and ink-jet method digital printers. Compared to a conventional offset printing, POD can handle a print job with a relatively small lot in a short delivery period and perform variable data printing (hereinbelow, referred to as VDP) making use of characteristics of using electronic data. A VDP document includes an object used in a fixed part (hereinbelow, referred to as a fixed object) and an object used in a variable part (hereinbelow, referred to as a variable object). Printing is performed by changing the variable object for each client, so that the VDP documents of which contents are different from each other can be printed. ISO 16612-2 portable document format/variable data and transactional (PDF/VT) has been issued as the language specification for variable printing.
PDF/VT is a page description language (PDL) based on PDF and has a high affinity for a work flow which handles PDF as print data. Generally, a very large number of records is included in a data source in VDP. In particular, for example, if one record includes 20 pages and there are 1000 records, PDF/VT includes page information of 20000 pages. In other words, it cannot be estimated sweepingly since a data amount of one page information piece depends on complexity (an amount of drawing data) of the page, however, if VDP includes many records, a large number of the page information pieces are also included, and thus an entire data amount would be very large.
Japanese Patent Application Laid-Open No. 2013-134748 discusses a method for separating VDP data into print data and a data source and combining the print data and the data source at the time of printing. In this method, the print data includes page information for one record and configuration information of a variable part which dynamically changes for each record, and the configuration information of the variable part is combined with the data source at the time of printing, so that a data amount is reduced to an amount of one record.
There is a print inspection technique which reads a print image of a print target and a print product by a scanner or the like and compares the read data pieces with each other to determine whether printing is normally performed. Japanese Patent Application Laid-Open No. 2012-000876 discusses a method for using different criteria in comparison of fixed parts and in comparison of variable parts with use of the above-described print inspection technique and a variable printing technique.
However, when an error occurs in image combining processing, an image including an error (abnormal data) is output as an image combining result in some cases. On the other hand, in the case of the variable printing which performs image combining immediately before printing as described in Japanese Patent Application Laid-Open No. 2013-134748, it is premised that image combining is normally performed. Thus, if an error occurs in combining processing of a print image, abnormal data as the error is regarded as the print image as it is, and an image obtained by reading a print product printed based on the print image by the scanner is the same as the print image when being compared with the print image and inspected, so that an inspection error does not occur. In other words, if the inspection processing is performed by the same method as the conventional method, there is a risk that a check on an inspection error does not function.
The present invention is directed to the provision of a print inspection apparatus capable of detecting an error in inspection processing of a print product even in a case where an error occurs when an image is combined in variable printing which performs image combining immediately before printing in consideration of the above-described issue.